Two Decades after Mandibuloacral Dysplasia Discovery: Additional Cases and Comprehensive View of Disease Characteristics

Pathogenic variants in the LMNA gene cause a group of heterogeneous genetic disorders, called laminopathies. In particular, homozygous or compound heterozygous variants in LMNA have been associated with “mandibuloacral dysplasia type A” (MADA), an autosomal recessive disorder, characterized by mandibular hypoplasia, growth retardation mainly postnatal, pigmentary skin changes, progressive osteolysis of the distal phalanges and/or clavicles, and partial lipodystrophy. The detailed characteristics of this multisystemic disease have yet to be specified due to its rarity and the limited number of cases described. Here, we report three unrelated Egyptian patients with variable severity of MAD features. Next-generation sequencing using a gene panel revealed a homozygous c.1580G>A-p.Arg527His missense variant in LMNA exon 9 in an affected individual with a typical MADA phenotype. Another homozygous c.1580G>T-p.Arg527Leu variant affecting the same amino acid was identified in two additional patients, who both presented with severe manifestations very early in life. We combined our observations together with data from all MADA cases reported in the literature to get a clearer picture of the phenotypic variability in this disease. This work raises the number of reported MADA families, argues for the presence of the founder effect in Egypt, and strengthens genotype–phenotype correlations.

Cutaneous and metabolic defects associated with nuclear abnormalities in a transgenic mouse model expressing R527H lamin A mutation causing mandibuloacral dysplasia type A (MADA) syndrome

LMNA gene encodes for lamin A/C, attractive proteins linked to nuclear structure and functions. When mutated, it causes different rare diseases called laminopathies. In particular, an Arginine change in Histidine in position 527 (p.Arg527His) falling in the C-terminal domain of lamin A precursor form (prelamin A) causes mandibuloacral dysplasia Type A (MADA), a segmental progeroid syndrome characterized by skin, bone and metabolic anomalies. The well-characterized cellular models made difficult to assess the tissue-specific functions of 527His prelamin A. Here, we describe the generation and characterization of a MADA transgenic mouse overexpressing 527His LMNA gene, encoding mutated prelamin A. Bodyweight is slightly affected, while no difference in lifespan was observed in transgenic animals. Mild metabolic anomalies and thinning and loss of hairs from the back were the other observed phenotypic MADA manifestations. Histological analysis of tissues relevant for MADA syndrome revealed slight increase in adipose tissue inflammatory cells and a reduction of hypodermis due to a loss of subcutaneous adipose tissue. At cellular levels, transgenic cutaneous fibroblasts displayed nuclear envelope aberrations, presence of prelamin A, proliferation, and senescence rate defects. Gene transcriptional pattern was found differentially modulated between transgenic and wildtype animals, too. In conclusion, the presence of 527His Prelamin A accumulation is further linked to the appearance of mild progeroid features and metabolic disorder without lifespan reduction.

Focal segmental glomerulosclerosis in patients with mandibuloacral dysplasia owing to ZMPSTE24 deficiency

BACKGROUND

Mandibuloacral dysplasia (MAD) is a rare autosomal recessive disorder characterized by skeletal abnormalities such as hypoplasia of the mandible and clavicles and acro-osteolysis. Other features include cutaneous atrophy and lipodystrophy. Two genetic loci are known for MAD: lamin A/C (LMNA), encoding structural nuclear lamina proteins, and zinc metalloproteinase (ZMPSTE24), a membrane-bound endoprotease involved in post-translational proteolytic cleavage of carboxy terminal residues of prelamin A to form mature lamin A.

METHODS

Mutational analysis of ZMPSTE24 in an additional patient with MAD and determination of functional activity of mutant ZMPSTE24 in a yeast growth arrest pheromone diffusion (halo) assay.

RESULTS

We previously reported a Belgian woman with MAD who had ZMPSTE24 mutations and died of complications of chronic renal failure at the age of 27.5 years. We now report a 37-year-old Australian man with MAD who also had compound heterozygous mutations in the ZMPSTE24 gene, a null mutation, Phe361fsX379, and a missense mutation, Asn265Ser, which is partially active in the yeast complementation assay. He also developed end-stage renal disease and, despite receiving a cadaveric renal transplantation, died prematurely at the age of 37 years. Renal biopsies of both patients revealed focal segmental glomerulosclerosis, and the female patient had the collapsing variant.

CONCLUSION

These observations suggest focal segmental glomerulosclerosis as a phenotypic manifestation in patients with ZMPSTE24 deficiency.

Early Marjolin's ulcer in Bureau-Barriere syndrome

Bureau-Barrière syndrome (BBS) describes a rare destructive process affecting skin and bone resulting from an acquired unilateral or bilateral polyneuropathy. Clinically, it is characterized by a triad of symptoms, namely, acral ulcerations, polyneuropathy, and bone lesions. To date, the development of Marjolin's ulcer in the course of BBS has not been described to the authors' knowledge.

Adult-onset idiopathic progressive acro-osteolysis with proximal symphalangism

We experienced a 57-year-old female with adult-onset non-congenital idiopathic acro-osteolysis combined with proximal symphalangism. At the age of 36, she developed severe pain and swelling of the toe base of both feet and underwent Clayton surgery. However, the size of her toes diminished progressively over the 5-year period after surgery. At the age of 41, she suffered pain and swelling of the proximal interphalangeal (PIP) joints of fingers of both hands. These PIP joints became rigid and inflexible. Subsequently, she noticed shortening of the little finger of both hands, followed later by shortening of the index, middle, and ring fingers. At the age of 57, the thumbs began to shorten. Laboratory and endocrinological examinations were not abnormal. Finally, we diagnosed her with acro-osteolysis combined with proximal symphalangism by radiological examination. In this case, previously unreported mutations of the Noggin gene were identified. This is the first case report of adult-onset, non-congenital idiopathic acro-osteolysis combined with proximal symphalangism.

Hemifacial microsomia, external auditory canal atresia, deafness and Mullerian anomalies associated with acro-osteolysis: a new autosomal recessive syndrome?

We report the combination of hemifacial microsomia, external auditory canal atresia, deafness and acro-osteolysis in several members of a highly consanguineous Asian family. In addition Mullerian anomalies have been found in two female members of the family. The external auditory canal stenosis and Mullerian anomalies in this family are similar to those reported by Winter et al. [(1968) J Pediatr 72 : 88-93] and overlap with those found in Goldenhar syndrome and Mullerian duct/renal aplasia/cervicothoracic somite dysplasia (MURCS), CHARGE and VATER associations. However, to the authors' knowledge, acro-osteolysis has not been reported in patients with any of these conditions. Overall, the findings in this family appear to be unique and the presence of consanguinity suggests an autosomal recessive condition with variable expression.